Omega Calibre 9605

I was fortunate enough to invest in a new Omega Seamaster Aqua Terra 150M Co-Axial Chronograph GMT recently and found that there was very little online information not only on this stunning timepiece, but the fantastic Omega in-house created movement, the Calibre 9605, living within. This post intends to shed a little more light on the capabilities of this movement and the Seamaster 231 reference models.

(Image courtesy of Omega)

A Brief History of Time (Keeping)

Omega is one of the most renown luxury watch makers in the world with a deep and storied history beginning in the 1840s. The famed Co-Axial movement, present in all Omega automatic watches, was brought to market in 1999 when Omega worked with genius watch-maker George Daniels who created the first new mechanical escapement the world had seen in 250 years. Many mechanical watches up to that point, and still to this day (Rolex), use the traditional lever escapement which make use of a lever with two ruby pallet stones pushed by the escape wheel. The escapement in a mechanical watch is what allows the power of the mainspring to be consumed in controlled manner while keeping near perfect time.

In a very simplified example, a tooth of the escape wheel is locked against a pallet stone that has a precise angle cut at the top, slowing the watch's gear train, until pushed to an unlocked position. This action of unlocking an escape wheel tooth sends an energy impulse back to the balance wheel causing it to swing back and forth with its own balance spring. The balance assembly in these movements are referred to as the "regulating organ" and are akin to a swinging pendulum in a pendulum clock. This motion causes the lever to pivot and lock the escape wheel using the opposite stone until pushed open by the next tooth of the escape wheel. This pushing of the balance wheel back and forth results in the frequency of the watch and determines its accuracy, typically 18,000 beats per hour, and is what produces the watch's ticking sound. The traditional lever escapement method requires lubrication of the pallet stones as friction is created when the escape wheel pushes against the angled pallet stones, 18,000 times per hour.

Daniels' design was different in that he used a modified lever fork with three pallet jewels driven by a modified double escape wheel fixed to the same axis (hence "co-axial") that separates the locking and impulse activities (rubies on fork: 1 impulse, 2 locking). This design also uses a modified balance with two additional impulse jewels, one for each direction of rotation. Most of the operation is handled by the larger lower wheel with the upper wheel receiving motion from the torque wheel but also sending a balance impulse during the anti-clockwise balance rotation. As the balance rotates clockwise, the entry pallet (on the far left of the fork) moves to an unlocked position and a tooth on the bottom wheel pushes the impulse jewel attached directly to the balance. When the balance completes its clockwise rotation, it swings anti-clockwise and the exit pallet (on the far right of the fork) moves to an unlocked position and a tooth from the top wheel pushes the jewel in the center of the fork. This pushes the lower impulse jewel attached directly to the balance by the end of the fork causing the balance to complete its anti-clockwise motion. The impulses to the balance wheel regulate the frequency of the watch and occur from both the upper and lower wheels depending on the rotational direction of the balance.

The expected result of the co-axial movement is an effective elimination of the sliding friction of the pallet stones over the escape wheel with what should ultimately result in less wear and lengthened service intervals. There is also a reduced need for pallet stone lubrication. Neat design but definitely a good deal more complex than the traditional lever escapement with several additional parts. Time will tell if the co-axial escapement is truly that much better but for now the experts agree that Omega has created something special and innovatively differentiated. Here's a great video from Omega detailing exactly how their Co-Axial movement functions: https://www.youtube.com/watch?v=2ID9bGj_gtY

(base image courtesy of Omega - I added labels)

Calibre 9605 Movement

Omega's Co-Axial calibre has evolved from what began as the 2500 to a fully in-house developed premium movement with several models and complications. The 9300 was Omega's first fully in-house made movement that would change the brand forever. Proving you can do it all under one roof is a big deal for a watch maker and as a consumer looking to invest in a premium timepiece. Omega boasts a few additional innovations which separate their watches from the competition. Omega features a free sprung balance that uses silicon for the balance wheel and balance spring which as a material is incredibly durable and resistant to magnetism. Magnets are the enemy of a mechanical watch and Omega has taken steps to reduce their effects, even more so with the new Master Co-Axial designation via the Swiss METAS certification. The 9605 is a COSC certified chronometer which is a label given to less than 3% of Swiss watches designating that a timepiece is made of the highest quality components and rigorously precision tested. Below is an image of the silicon balance wheel (Si14), balance spring and co-axial escapement.

This movement uses a twin barrel mainspring with a slipping clutch in the second barrel to prevent over-winding and is able to provide a 60 hour power reserve drawing from both barrels. This design aspect is also intended to prevent loss of accuracy over time due to any decreased torque when the watch is operating on its power reserves. The 9605 is also outfitted with a traditional column wheel for chronographic functions (start, stop, reset). The weighted rotor on the outermost portion of the movement drives the automatic winding mechanism and can wind the mainspring turning in either direction. The image below is the back of my Seamaster AT showing the balance bridge, 2nd barrel, column wheel and weighted rotor of the 9605 movement, stunningly finished in rhodium plating styled with "Geneva waves in arabesque." Fantastic doesn't begin to describe this remarkable piece.

Calibre 9605 Functions

The 9605 movement has a fancier twin called the 9615. The movements are identical in function but the 9615 uses gold for some pieces of the movement visible through the transparent case back. The 9605 features four complications in addition to the basic time function: chronograph, date, GMT, 12 hour and 60 minute recorders. This is an incredible tool for traveling! The GMT hand lives with the small seconds hand at 9:00. This small seconds hand is the primary seconds hand for the watch and will always be spinning when the watch is wound. For small seconds the 24 marker of the dial = 60 and the 12 marker = 30. The The sweep seconds hand on the main dial is controlled by the upper chronograph pusher and can run all the time if desired or function as a stopwatch.

The 12 hour and 60 minutes recorder hands at the 3:00 subdial is also controlled by the chronograph function via the upper chronograph pusher. This 12-hour subdial at 3:00 can be used to track a specific number of hours or minutes but it can also be used when travelling to another time zone. Simply start the chronograph function when the local time is noon or midnight. The local time will now be tracked via this subdial with the main dial representing the time back home. This is the easiest way to track two time zones while travelling. Alternatively the time on the main dial can be adjusted to reflect the local time. The lower pusher is used to reset the sweep seconds and 3:00 subdial only once the chronograph function has been stopped via the upper pusher.

Another useful feature when considering different time zones is the GMT hand in the subdial at 9:00. This hand should always point to GMT/ UTC and is used to calculate the time in another time zone. Simply add or subtract hours based on the offset of the other time zone in question (example, GMT-6). The date is fairly self explanatory but should be noted that Omega uses a gradual change mechanism that will slowly shift the date displayed between the hours of 9pm and 2am each day. Make sure to never manually adjust the date during these hours as damage could occur.

The crown has three positions once unscrewed, pulled directly outward.

The first position is to manually wind the mainspring for extra power. If the mainspring completely unwinds due to lack of use, you will use this position to restart the watch, ~30 turns of the crown. You can also manually wind if you haven't worn the watch for a few days and want to tighten the mainspring. Never wind the watch while on your wrist!

The second position is used to adjust the hour hand on the main dial. When this hand crosses midnight it will change the date.

The third position is used to adjust the minute hand on the main dial. Turning this position will also adjust the GMT hand in the 9:00 subdial. Make sure you are on the 'correct' side of midnight when adjusting the GMT hand.